Between the 1920s and 1930s, a lot of conflicts were going on in the world much of which included the chancellor of Germany, Adolf Hitler. 

I am Adolf Hitler

America knew about the troubles going on in Germany, such as the cruel circumstances many Jews were facing. However, America decided they didn't want to get involved and would rather become isolated .

We should not get involved with international problems

America didn't want to get involved with global conflict that did not involve them. For example, many Jews tried to escape Germany fleeing to safety in America but President Roosevelt refused to pass bills that would help them migrate to America, and he sent them away instead. 

You cannot come!

To maintain peace and isolationism, America created something called the Neutrality Acts which banned transportation and certain connections with aggressive nations typically in war.

One example of these acts is something called "Cash and Carry". It was a way for America to stay out of the conflict but help allied countries in war. It allowed nations at war to purchase war material if they could pay cash for it and arrange for its transportation onboard their ships.